System for converting existing tankers to shuttle tankers

ABSTRACT

A system for converting Jones Act/OPA90 compliant tankers to shuttle tankers includes a dynamic positioning system, means for bow loading of crude oil, and the necessary power systems to make each operational.

BACKGROUND OF THE INVENTION

[0001] Reference to Related Application

[0002] This application claims priority from U.S. Provisional Patent Application Ser. No. 60/435,142 filed Dec. 20, 2003.

FIELD

[0003] The present invention pertains to a system for converting existing tankers into shuttle tankers; more particularly, the present system describes a system for converting existing tankers including the required systems to be compliant with the Jones Act and with the OPA90 into shuttle tankers for moving crude oil from offshore locations to either storage facilities or refineries located on shore.

BACKGROUND

[0004] In recent years, the United States has placed special restrictions on the type of tanker vessels that may be used in the transport of crude oil from offshore locations such as production platforms to onshore storage facilities or refineries. Two of the more stringent sets of specifications for vessels involved in coastal shipping operations appear in the Federal Law which is known as the “Jones Act” (46 USC 883) and in the Oil Pollution Act of 1990 (OPA90) (33 USC 2701). Thus, in order for an operator of a tanker to use a tanker to shuttle crude oil produced by coastal wells from an offshore production platform to an onshore facility in the U.S., it is necessary that the tanker be compliant with both the Jones Act and with OPA90. Tankers which do not comply with the Jones Act or with OPA90 simply cannot be used.

[0005] Because of the many technical and operational requirements associated with both the Jones Act and with the OPA90, few tanker vessels exist which satisfactorily comply with all requirements. It has been thought by many that it would be necessary to design and build entirely new tankers to carry crude oil produced by offshore production platforms into U.S. coastal waters for offloading at U.S. ports. Some have estimated the time to design and build new Jones Act and OPA90 compliant tankers to be at least three years. In addition to the long design and build time, the cost of building a new Jones Act compliant and OPA90 compliant tanker is prohibitive for most tanker operators.

[0006] On the opposite side of the problem is the fact that existing Jones Act/OPA90 compliant vessels are not entirely suitable for use as short haul shuttle tankers in bodies of water such as the U.S. Gulf of Mexico.

[0007] Accordingly, there is a need in the art to convert existing Jones Act/OPA90 compliant vessels into vessels, typically called shuttle tankers, which can be used for the transport of crude oil produced in U.S. coastal waters to U.S. ports.

SUMMARY

[0008] Disclosed herein is a system for converting recently built (e.g., five years old or less) tankers which are compliant with the requirements of the Jones Act and compliant with the requirements of OPA90 into shuttle tankers for use in the transport of crude oil in U.S. coastal waters.

[0009] The kit which would convert a Jones Act compliant, OPA90 compliant tanker into a vessel suitable for shuttle tanker service in U.S. coastal waters would include the addition of a dynamic positioning system, to include an auxiliary propulsion system around its hull, a bow loading system for receiving crude oil, and the necessary power and control systems for each.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0010] A better understanding of the system for converting existing Jones Act OPA90 compliant tanker vessels to shuttle tankers may be had by reference to the drawing figures, wherein:

[0011]FIG. 1 is a schematic plan view of the relative position of a shuttle tanker, including the kit of the present invention, with respect to a floating crude oil storage and offloading vessel; and

[0012]FIG. 2 is an elevational view of the vessels shown in FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

[0013] The use of a dynamically positioned floating storage and off-loading vessel with shuttle tankers is described in the attached drawing figures. Rather than building a new ship which is designed to be Jones Act compliant and OPA90 compliant, the present invention describes a kit of equipment which can be placed on a Jones Act compliant, OPA90 compliant tanker to make it suitable for service as a shuttle tanker for use in U.S. coastal waters.

[0014] In FIG. 1 is shown an offshore production platform 10. A dynamically positioned floating crude oil offloading and storage vessel 20 is connected to the platform 10 by a flexible transfer hose 22. The purpose of the dynamically positioned floating crude oil offloading and storage vessel is to receive and temporarily hold crude oil for offloading to a shuttle tanker 50. The illustrated system is often called tandem loading, wherein the long axes of the vessels 20 and 50 are generally parallel. The flexible transfer hose 35 for conveying the crude oil from vessel 20 to shuttle tanker 50 is generally stored on vessel 20. Shuttle 50 includes a bow connection system 52 for connection to the transfer hose 35.

[0015] A still better understanding of the system appears in FIG. 2. Essential to the use of a shuttle tanker 50 is its ability to maintain a proper angular orientation and separation distance from the floating crude oil offloading and storage vessel 20 while the floating crude oil offloading and storage vessel 20 maintains a safe separation distance from the offshore platform 10. The ability of the shuttle tanker 50 to control its position in the water is provided by a computer controlled dynamic positioning system. This computer controlled dynamic positioning system includes 56 thrusters positioned around the hull of the shuttle tanker and computer control of the main propulsion and rudder systems 54.

[0016] In a dynamic positioning system, it is necessary that the shuttle tanker 50 have the capability to both maintain its angular orientation and separation distance with respect to another object such as a dynamically positioned floating storage and offloading vessel (DPFSO) 20 as shown in FIGS. 1 and 2.

[0017] To properly position a shuttle tanker 50, a signal is provided which is representative of the distance of the shuttle tanker 50 from the floating storage and offloading vessel 20. This signal is used to provide an input to the computer controlled dynamic positioning systems on board the shuttle tanker 50 to assure that the shuttle tanker is properly moved to maintain a constant angular orientation and separation distance with respect to the floating storage and offloading vessel 20. Alternatively, the dynamic positioning system may be used to assure that the shuttle tanker 50 maintains a constant position with respect to a point on the earth's surface using GPS or an equivalent location determination system.

[0018] Because the position of a vessel at sea is determined not only with respect to the position of its center of mass with respect to another object or a fixed location on the earth's surface, but the position of a vessel at sea is also determined by the orientation of its long axis in response to the effects of the forces F of wind and waves on the ship, it is necessary that the vessel include control systems to regulate both the auxiliary positioning systems 56 such as thrusters positioned around the hull of the shuttle tanker 50 and the main propulsion and rudder system 54 of the shuttle tanker 50. Control of the auxiliary positioning systems 56, together with the main propulsion and rudder system 54, allows for maintaining both the position of the center of mass of the vessel and the angular orientation of the long axis of the vessel within predetermined limits. The signals which control the operation of the thrusters 56 located around the hull are obtained from the dynamic positioning system. The nature of the construction of the thrusters 56 allows for controlling and directing the forces placed on the hull to accurately position and orient the shuttle tanker 50.

[0019] Further, it is expected that the offloading of the crude oil from the floating storage and offloading vessel will be through fluid connections mounted on the front of the shuttle tanker 50. Thus, it will be necessary to position the bow of the shuttle tanker at a proper orientation and separation distance with respect to the floating storage and offloading vessel 20. A flexible fluid conduit 35 from the floating storage and offloading vessel will be connected to a bow loading system 52 in the front of the shuttle tanker 50. Once this connection is made with the bow loading system 52, pumping operations will be initiated whereby crude oil from the tanks on the floating storage and offloading vessel 20 will pass through the flexible fluid conduit 35 to the tanks in the shuttle tanker 50.

[0020] Therefore, to convert a Jones Act/OPA90 tanker to shuttle tanker service, it is necessary to add a bow connection system 52 and a dynamic positioning system for control of the thrusters 56 and the main propulsion and rudder system 54. Further, it will also be necessary to add special power sources to drive both the thrusters located on the ship's hull and the system which connects the bow of the shuttle tanker 50 to the floating storage and offloading vessel 20. For ease of construction, these power sources may be placed on the deck or within the shuttle tanker 50.

[0021] Existing or enhanced systems on board the shuttle tanker will be able to determine crude oil flow, tension in the flexible hose connection between the floating storage and offloading vessel and the shuttle tanker, completion of necessary fluid flow connections, and the condition of the crude oil storage tanks.

[0022] While the present system and method has been disclosed according to the preferred embodiment of the invention, those of ordinary skill in the art will understand that other embodiments have also been enabled. Such other embodiments shall fall within the scope and meaning of the appended claims. 

What is claimed is:
 1. A kit for converting a Jones Act compliant, OPA90 compliant tanker into a shuttle tanker for use with a floating storage and offloading vessel, said kit comprising: a dynamic positioning system for: ascertaining the position of the tanker and then determining the movement required from said ascertained position to a predetermined position; means for moving said tanker from said ascertained position to said predetermined position; means for loading fluids from said floating and storage and offloading system to said tanker, said system for loading fluids constructed and arranged to be located at the bow portion of the tanker; power means for driving said means for moving said tanker and said means for loading fluids.
 2. The kit as defined in claim 1 wherein said tanker further includes at least one thruster mounted to the hull of the tanker.
 3. A method for converting a Jones Act compliant, OPA90 compliant tanker into a shuttle tanker for use with a floating storage and offloading vessel, said method comprising the steps of: adding a plurality of thrusters at various locations around the hull of the shuttle tanker; controlling said plurality of thrusters and the main propulsion and rudder system of the shuttle tanker to maintain the shuttle tanker in a predetermined position; adding a bow loading system to the front of the shuttle tanker. 